1. Field of the Invention
The present invention relates to a disk-chucking apparatus for disk drives, and more particularly to a disk-chucking apparatus for disk drives wherein the distance from the center of a disk to the rotational center of a driving shaft is minimized, and the assembly of a motor and a chuck base is easily and rapidly carried out without using a bonding agent.
2. Description of the Related Art
Generally, a disk drive comprises: a deck base forming a main body of the disk drive; means for loading/unloading a disk to/from the deck base; means for rotating the disk loaded to the deck base by means of the loading/unloading means at a predetermined speed; and means for reading/writing information from/to a recording surface of the disk while the reading/writing means moves in the radial direction of the disk rotated by the rotating means. The disk may be loaded or unloaded while being placed on a tray. Also, the disk may be introduced into or withdrawn from the inside of the deck base while being received in a caddy or a cartridge.
A spindle motor is usually used as the disk rotating means, and a pick-up unit is usually used as the reading/writing means.
The disk drive as described above further comprises a disk-chucking apparatus that prevents the disk from being separated from the spindle motor when the motor is rotated at a predetermined speed while being rotated along with the disk for assuring safety of the disk rotated in one direction by means of a rotary force of the motor. The chucking performance of the disk-chucking apparatus is a critical aspect of disk drive technology.
FIG. 1 is a plan view showing a conventional disk-chucking apparatus 1 for disk drives. As shown in FIG. 1, the conventional disk-chucking apparatus 1 comprises: a chuck base 2 fixedly mounted to the upper surface of a turntable or a rotary case 9 rotatable by means of a driving force of a motor (not shown) such that a disk D can be fitted on the chuck base 2 through a center hole C of the disk D; a plurality of chuck pins 3 disposed in a plurality of disposition parts 2a formed at the outer surface of the chuck base 2 while being uniformly spaced apart from each other in the circumferential direction of the chuck base 2, respectively, while being movable inward and outward; a plurality of resilient pieces 4 formed at the chuck base 2 between the disposition parts 2a of the chuck base 2 for resiliently supporting the disk D fitted on the chuck base 2 at the inner circumference of the center hole C of the disk D; and a plurality of spring members 5 disposed in the disposition parts 2a of the chuck base 2 for resiliently pushing the chuck pins outward. Unexplained reference numeral 8 indicates a board on which the motor is mounted.
A method for chucking the disk D by means of the conventional disk-chucking apparatus 1 as described above will now be described. When the disk D is pushed downward onto the chuck base 2, the lower edge of the inner circumference of the center hole C of the disk D comes into contact with the chuck pins 3, respectively, since the outer diameter of the chuck base 2 is slightly less than the inner diameter of the center hole C of the disk D while the outer parts of the chuck pins 3 disposed in the disposition parts 2a of the chuck base 2 are slightly protruded outward.
The outer parts of the chuck pins 3 are tapered such that the upper surfaces of the outer parts of the chuck pins 3 are gently inclined downward, respectively. Consequently, the chuck pins 3 are withdrawn inward while compressing the corresponding spring members 5 by means of a fitting force vertically applied to the disk D. At the same time, the resilient pieces 4 are also withdrawn inward.
When the disk D comes into contact with a rubber ring disposed at the upper surface of the rotary case 9, the disk D is maintained while being fitted on the chuck base 2 through the cooperation of the chuck pins 3 pushed outward by a resilient restoring force generated when the spring members 5 are compressed and the resilient pieces 4 having their own resilient restoring forces.
The fitting force required to fit the disk D onto the chuck base 2 of the disk-chucking apparatus 1 is determined depending upon the resilient forces of the spring members 4 that resiliently support the chuck pins 3 outward. The spring members 5 disposed in the respective disposition parts 2a of the chuck base 2 while corresponding to the chuck pins 3, respectively, preferably have the same resilient force. In fact, however, it is difficult to manufacture the spring members 5 such that the spring members 5 have the same resilient force.
When the spring members 5 do not have the same resilient force, and thus when even one of the chuck pins 3 disposed in the disposition parts 2a of the chuck base 2 while being pushed outward by means of the spring members has a relatively large resilient force, the disk D is eccentrically moved toward the chuck pin(s) 3. As a result, the center of the disk D does not exactly correspond to the rotational center of the motor. Specifically, the distance from the center of the disk D to the rotational center of the motor is increased.
When the distance from the center of the disk D to the rotational center of the motor is small, an optical pick-up unit smoothly reads or writes data from or to the disk D with a low error rate. Consequently, decreasing the distance from the center of the disk D to the rotational center of the motor, i.e., aligning the center of the disk D with the rotational center of the motor is very important for the ODD motor.
FIG. 2A is a plan view showing a chuck base of the conventional disk-chucking apparatus for disk drives shown in FIG. 1, and FIG. 2B is a longitudinal sectional view showing the chuck base of the conventional disk-chucking apparatus for disk drives shown in FIG. 1.
As shown in FIGS. 2A and 2B, the resilient pieces 4 are formed, in large numbers, at the chuck base 2 between the disposition parts 2a of the chuck base 2 where the corresponding chuck pins 3 are disposed for generating resilient forces outward to minimize the distance from the center of the disk D to the rotational center of the motor.
When the resilient forces of the spring members are increased to prevent the disk D from being separated from or slipping off the chuck base 2, and thus the detaching force required to detach the disk D from the chuck base 2 is increased, automatic aligning function of the resilient pieces 4 to align the center of the disk D with the rotational center of the motor may be deteriorated or lost, since the resilient forces generated from the resilient pieces 4 each having a curved part 18 formed, with predetermined outer and inner curvatures 18a and 18b, at the interface between a horizontal resilient part 14a and a vertical resilient part 14b is less than those of the spring members 5. As a result, errors may frequently occur when the pick-up unit reads or writes information from or to the recording surface of the disk D.
When the distance from the center of the disk D to the rotational center of the motor is increased, the moved amount of the pick-up unit is increased, and thus the consumed amount of electric current, necessary to move the pick-up unit, is also increased.
The inner curvature 18b of the curved part 18, which is formed at the inner edge of each of the resilient pieces 4, is equal to or less than the outer curvature 18a of the curved part 18, which is formed at the outer edge of each of the resilient pieces 4. Consequently, the thickness of the vertical resilient part 14b is decreased as the center C1 of the inner curvature 18b approaches each of the resilient pieces 4 with the result that the resilient force of each of the resilient pieces 4 is decreased, and thus the resilient pieces 4 may be easily broken by an external force.
The radius of curvature of each resilient piece 4, the outer surface of which contacts the inner circumference of the center hole C of the disk D, is equal to that of the center hole C of the disk D. Consequently, a large frictional force occurs as the outer surface of each resilient piece 4 comes into contact with the inner circumference of the center hole C of the disk D with the result that it is very difficult to smoothly fit the disk D onto the chuck base 2 or detach the disk D from the chuck base 2.
In order to fit a driving shaft 20 of the motor into a fitting hole 15 formed through the center of the chuck base 2, a bonding agent is applied to the inner circumference of the fitting hole 15 of the chuck base 2 or the outer circumference of the driving shaft 20 of the motor, and then the driving shaft 20 is inserted into the fitting hole 15. As a result, the driving shaft is fixedly attached to the chuck base 2 by means of the bonding agent.
As described above, a bonding agent is applied to the inner circumference of the fitting hole 15 of the chuck base 2 or the outer circumference of the driving shaft 20 of the motor in order to fit the driving shaft 20 of the motor into the fitting hole 15 of the chuck base 2. Consequently, the assembly of the conventional disk-chucking apparatus is complicated and troublesome, and the cost of manufacturing the conventional disk-chucking apparatus is increased.
The bonding force of the bonding agent applied between the fitting hole 15 and the driving shaft 20 is easily decreased due to external temperature variation or external impact. Also, the chuck base 2 is easily separated from the driving shaft 20 of the motor as the disk D is repetitively fitted onto the chuck base 2 and detached from the chuck base 2.
Furthermore, the disk D is eccentrically moved due to the bonding agent applied to the gap between the fitting hole 15 and the driving shaft 20. As a result, the distance from the center of the disk D to the rotational center of the driving shaft 20 is increased, whereby errors frequently occur during reading/writing data from/to the disk D. Also, the moved amount of the pick-up unit is increased.
At the lower edge of the chuck base 2 are formed thin flanges 17, which extend outward. Each of the flanges 17 is provided at the inner side thereof with a pin-supporting member 13 for supporting the lower end of the corresponding chuck pin 3, which is pushed downward when the disk D is fitted onto the chuck base 2.
However, an external vertical downward force, which is generated as the chuck pins 3 come into contact with the pin-supporting members 13 when the disk D is fitted onto the chuck base 2, is focused on connection regions between the pin-supporting members 13 and the flanges 17, by which the connection regions are broken.